Well water and health: Treat your well water

What to do if your well water contains bacterial or chemical contaminants.

On this page

• What to do if your well is contaminated
• How to shock disinfect your well
• Treatment systems
• Examples of NSF/ANSI certified treatment systems

What to do if your well is contaminated

Your water test results may show that contaminants in your well water are above drinking water guidelines. If so, take corrective action to eliminate or reduce the levels of contaminant present.

It's important to identify the source of contamination. If you find the source, remove or fix the problem to prevent it from happening again. You will need to shock treat your well to remove microbial contamination.

If you can't find or fix the cause of contamination, then you should consider:

• installing a new well
• installing a treatment system
• finding a different supply of safe drinking water

Different sources of contamination

How to shock disinfect your well

If your well is contaminated with E. coli, you need to shock disinfect your well to help remove any harmful microbial contaminants. If it's your first time shocking your well, you can hire a licensed well contractor to help you.

Note that the water will need to sit in the plumbing system for 12 to 24 hours. If you plan to stay in your home during this time, you should have a back-up source of water for drinking and cooking. You may also want to fill your tub with water to use for household activities such as toilet flushing.

You will need:

• safety glasses
• rubber gloves
• a wrench or pliers
• a funnel
• unscented 5.25% liquid household bleach
  • Don't use swimming pool or hot tub disinfectants. These contain other chemicals that you don't want in your well.
• a garden hose that can reach your well

Gather information about your well, including the:

• overall depth
• diameter of the well casing
• water level inside the well casing (static water level)

You should be able to find this information on your copy of the well contractor's report. Alternatively, look for an identification tag on your well. You can use the well tag number to find a copy of the report:

• in your province or territory's online well database
• by contacting the water quality authorities in your area

Step-by-step instructions

Once you have gathered all the necessary supplies, you're ready to shock treat your well:

1. Determine the amount of bleach you will need for your well. The calculations are based on regular, unscented 5.25% household bleach found in most grocery stores.
   • Use this formula to calculate the depth of water in your well: the well's overall depth minus the static water level.
   • Use the water depth and Table 1: Amounts of bleach needed for shock treatment to determine how much bleach you'll need.

2. Turn or push bypass valves for any water treatment devices you have installed such as softeners, filters or reverse osmosis systems. Chlorinated water from shock chlorination may damage these systems.
3. Turn off electrical power to the well pump. Wires may be exposed once the well cap, cover or seal are removed. There's risk of electrical shock when working with water near electricity.
4. To access the well, remove the well cap, cover or seal.
   • You may need a wrench or pliers to remove a few bolts.
   • Some wells that have been installed in a well pit have a seal with a pump or intake lines that are held in place by the seal. In this case, it may be possible to use the vent hole or remove a plug in order to add chlorine bleach to your well.
5. Use a funnel to pour the unscented bleach into the well.
   • Always use gloves and safety goggles when handling bleach as it contains chlorine.
   • Be careful to avoid any electrical connections.
   • Rinse the bleach off the well wall and components with fresh unchlorinated water to prevent corrosion.
6. Turn the electricity to the well pump back on. Be careful: wires at the well head are now energized.
7. Connect a clean garden hose to the faucet closest to the well. The hose must be able to reach into your well casing.
   • Turn on the water so it flows away from any nearby wells, septic systems, plants or surface waters.
   • Let the water run until there is a strong smell of chlorine in the water coming from the garden hose. If the water doesn't smell strongly of chlorine, add more bleach to the well and repeat.
8. Once there's a strong smell of chlorine, turn the hose off, place the end of the hose inside your well casing and turn the water back on.
   • Recirculate the chlorinated water in the well for 30 minutes.
   • If you want, use a chlorine test strip to confirm that the chlorine concentration is the targeted 50 mg per litre.
9. Turn off the hose, head inside and turn on the taps. Let the water run until the strong smell of chlorine is detected, then turn the tap off.
• Repeat this process for the cold and hot water for all the faucets including includes showers, tubs and toilets.
10. Allow the water to sit in the plumbing system for 12 to 24 hours.
• Don't drink, cook, bathe or wash with the water during this time. This ensures thorough disinfection and will prevent irritation caused by high levels of chlorine.
11. Clear the bleach from the well by turning on an outdoor hose and letting it run until the smell of chlorine is gone.
    • Make sure the water flows away from any nearby wells, septic systems, plants or surface waters.
    • Make sure that the chlorinated water doesn't enter any surface waters such as a lakes, rivers, ponds or streams.
12. Clear the bleach from the household plumbing by opening all indoor taps, hot and cold, until the water no longer smells of chlorine.
13. After 48 hours, collect and submit a water sample using the instructions and the bottle provided by the laboratory.
    • In the meantime, bring water to a rolling boil for 1 minute before drinking it or find another safe water source.
    • The treatment has probably worked if you get 2 "safe" tests in a row over a period of 1 to 3 weeks.
    • You should test 1 more sample after 3 to 4 months to be sure that the water hasn't become contaminated again.
    • If you don't get 2 safe water test results in a row, repeat the shock chlorination process. Inspect your well and property to look for potential sources of contamination.
    • Contact your local public health unit or drinking water authority if your water test results continue to have E. coli ortotal coliform bacteria.
14. Once your water quality tests show that your water is no longer contaminated with E.coli or total coliform bacteria, you can use your well water as usual.
    • Follow the manufacturer's instructions for cleaning any treatment devices or appliances before reconnecting them use.

Different sources of contamination

Treatment systems

You may want to look at treatment options if:

• the problem is recurrent
• you can't identify or remove the source of contamination

Treatment systems allow you to continue to use your well water safely by removing the contaminants from the water.

Find a reputable water treatment dealer to advise you on the best method to use based on your needs and water quality testing results. Ask whether you need a:

• point-of-use system, which treats water at a single tap
• whole home system, also called a point-of-entry system, which treats all water entering your home

Choose a treatment device certified to the right NSF/ANSI standard for treating your specific well water quality problems.

• Check the information included by the manufacturer to find out which microorganisms or chemicals it's certified to remove.
• There should be a symbol from an accredited certification body showing that the system meets the appropriate NSF/ANSI standards.

Once the treatment system has been installed, use an accredited laboratory to test the water entering and exiting the water treatment device. This will confirm whether the system is removing the desired contaminants.

To keep your treatment system working effectively, use and maintain it according to manufacturer's instructions.

Infographic: Finding a drinking water filter for lead

Examples of NSF/ANSI certified treatment systems

This section includes examples of NSF/ANSI certified treatment systems for common contaminants such as:

• lead
• nitrite
• nitrate
• copper
• arsenic
• manganese
• viruses
• bacteria
• protozoa

This isn't an exhaustive list of devices or the contaminants they can treat. If you're looking for a contaminant that isn't listed here, check its guideline document for advice.

Water quality reports and publications: Water Talks guidance and fact sheets

Ultraviolet light - Class A

NSF/ANSI standard 55

Treats: Bacteria, viruses, protozoa.

Important notes: Class A systems can be used to disinfect your well water in order to reduce microorganisms. Particles in the water can block the ultraviolet rays and prevent disinfection. Water should be treated with a filter (NSF/ANSI 53) before ultraviolet treatment.

Filtration

There are 2 standards for filters, with each treating different contaminants.

NSF/ANSI standard 53

Treats: Protozoa, pentavalent arsenic, lead, copper.

Important notes: Carbon filters are the most common type of filter covered by NSF/ANSI 53.

Only removes pentavalent arsenic (arsenic V). Other forms of arsenic may not be removed. Check the type of arsenic present in your well water.

NSF/ANSI standard 42

Treats: Manganese, removes particles.

Important notes: This standard addresses aesthetic issues only, including the aesthetic objective for manganese.

Reverse osmosis

NSF/ANSI standard 58

Treats: Protozoa, nitrate, nitrite, pentavalent arsenic, manganese, lead, copper

Important notes: Only removes pentavalent arsenic (Arsenic V). Other forms of arsenic may not be removed. Check the type of arsenic present in your well water.

Manganese removal has recently been added to the standard. Although reverse osmosis is effective for removal of this contaminant, certified devices may not yet be available.

Distillation

NSF/ANSI standard 62

Treats: Bacteria, viruses, protozoa, nitrate, nitrite, arsenic, lead, copper, manganese.

Important notes: Designed to decrease specific chemicals and microorganisms.

Cation exchange softeners

NSF/ANSI standard 44

Treats: Hardness.

Important notes: Softeners are mainly used to remove natural water "hardness," caused by calcium or magnesium. Since softeners add some salt to your water, it's recommended that you by-pass your kitchen faucet. This will help avoid the extra salt in your food or drinking water.